COLREGS Rule 30 — Navigation Lights
Vessel Aground — Navigation Lights (COLREGS Rule 30)
A vessel aground shows all the anchor lights appropriate for its length, plus two additional all-around red lights in a vertical line. By day it shows anchor ball(s) plus three black balls in a vertical line. The two red lights are what distinguish a vessel aground from one merely anchored.
Condition: Hard aground, at any time
Navigation lights required
| Light | Color | Arc | Position |
|---|---|---|---|
| Anchor light(s) — as for vessel at anchor | White | 360° | One all-around white (< 50 m); forward higher + aft lower (≥ 50 m) |
| All-around red light (upper) | Red | 360° | Upper of two vertical all-around red lights |
| All-around red light (lower) | Red | 360° | Lower of two vertical all-around red lights |
Anchor light(s) — as for vessel at anchor: Full anchor light configuration for the vessel's length, as required by Rule 30(a–b), shown in addition to the two red lights
All-around red light (upper): Shown in addition to — not instead of — the anchor lights
All-around red light (lower): Shown in addition to the anchor lights
Dayshapes
| Shape | Position | When displayed |
|---|---|---|
| Three black balls in a vertical line | Where they can best be seen | During daylight hours when aground — shown instead of (and distinct from) the single anchor ball |
Exceptions and size rules
- →A vessel aground may also illuminate its decks using working lights.
- →Vessels under 12 m that are aground are not required to show the aground lights and shapes.
Inland Rules differences
- !US Inland Rules require the same signals for a vessel aground — no practical difference.
Common exam mistakes
- ✗Forgetting the anchor lights — an aground vessel shows BOTH anchor lights AND two red lights, not just the two red lights alone.
- ✗Confusing the aground dayshape (three balls) with the NUC dayshape (two balls) or anchor dayshape (one ball).
- ✗Confusing aground lights with NUC lights — both show two all-around red lights, but an aground vessel also shows anchor lights; NUC does not.
- ✗Thinking aground signals replace anchor signals — they are additive: anchor lights PLUS two red lights.
USCG exam questions — Vessel Aground
These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.
1. A vessel at anchor shall show by night:
- A.An all-round white light where it can best be seen
- B.An all-round white light forward and an all-round white light aft, the after light being lower✓
- C.Sidelights and an all-round white light
- D.A flashing white light
Why: Rule 30(a) requires an anchored vessel to show an all-round white light in the fore part of the vessel and a second all-round white light at or near the stern, lower than the forward light. This two-light combination helps observers judge the vessel's length and orientation.
2. A vessel less than 50 meters in length at anchor may, instead of the two prescribed anchor lights, show:
- A.A flashing white light
- B.A red over white all-round light
- C.A single all-round white light where it can best be seen✓
- D.Sidelights only
Why: Rule 30(b) allows vessels less than 50 meters at anchor to show just one all-round white light where it can best be seen, instead of the two-light forward/aft arrangement required for larger vessels.
3. A vessel aground at night shall show the anchor lights PLUS:
- A.Two all-round red lights in a vertical line✓
- B.A red flashing light
- C.Three all-round red lights in a vertical line
- D.A ball-diamond-ball sequence
Why: Rule 30(d)(i) requires a vessel aground to show the appropriate anchor lights (one or two all-round white lights) PLUS two all-round red lights in a vertical line. These red lights warn other mariners that the vessel is not merely at anchor but is stranded and completely immovable.
4. By day, a vessel aground shall display:
- A.Three black balls in a vertical line✓
- B.Two black balls in a vertical line
- C.A cylinder shape
- D.A black ball and a cylinder
Why: Rule 30(d)(ii) requires a vessel aground to display three black balls in a vertical line by day. This contrasts with the anchor shape (one black ball) or NUC (two balls), making three balls the unambiguous 'stuck on the bottom' signal.
5. By day, a vessel at anchor shall display:
- A.One black ball in the fore part of the vessel✓
- B.Two black balls in a vertical line
- C.A black cone, apex downward
- D.A black cylinder
Why: Under COLREGS Rule 30(a)(i), a vessel at anchor shall exhibit in the fore part, where it can best be seen, an all-round white light or one ball — so by day the required shape is a single black ball forward. (Two/three balls and the cone or cylinder denote other conditions: three vertical balls = aground per Rule 30(d), a cone apex-down = a sailing vessel proceeding under sail and power per Rule 25(e), and a cylinder = a vessel constrained by her draft per Rule 28.)
6. A vessel of 50 meters or more in length at anchor shall exhibit which lights?
- A.A forward all-round white light and an aft all-round white light lower than the forward one✓
- B.A single all-round white light visible all around the horizon
- C.Two all-round white lights of equal height
- D.A forward all-round white light and an all-round red light aft
Why: Rule 30(a) requires a vessel of 50 meters or more at anchor to exhibit a white all-round light forward and a second all-round white light at or near the stern at a lower height than the forward light, creating a distinctive anchor light profile.
7. A vessel aground shall exhibit which lights in addition to the anchor lights prescribed by Rule 30?
- A.Two all-round red lights in a vertical line✓
- B.Two all-round red lights and sidelights
- C.Three all-round red lights in a vertical line
- D.One all-round red light
Why: Under COLREGS Rule 30(d)(i), a vessel aground exhibits the anchor lights required by Rule 30(a) or (b) plus two all-round red lights in a vertical line (and, by day, three balls in a vertical line per 30(d)(ii)). These are a status signal identifying the vessel as aground — not a distress signal (distress signals are separately listed in Annex IV) — and do not denote not-under-command or restricted ability to maneuver under Rule 27.
8. A vessel aground during daylight hours must display which dayshapes?
- A.Three balls in a vertical line✓
- B.Two balls in a vertical line
- C.A single ball
- D.A ball above a diamond
Why: Under COLREGS Rule 30(d)(ii), a vessel aground exhibits three balls in a vertical line as her dayshape (in addition to her anchor lights/shape), distinct from the single ball shown by a vessel at anchor under Rule 30(a)(i). The three-ball signal marks the vessel as aground and unable to maneuver. (Vessels under 12 m aground are exempted by Rule 30(f).)
Frequently asked questions
- What lights does a vessel show when aground?
- A vessel aground shows all the anchor lights appropriate for its length (one all-around white for vessels under 50 m; two — forward higher and aft lower — for vessels 50 m or more) plus two additional all-around red lights in a vertical line. The two red lights are shown in addition to, not instead of, the anchor lights.
- How do you tell a vessel aground from a vessel that is simply anchored?
- Both show all-around white anchor light(s). A vessel aground also shows two all-around red lights in a vertical line — anchored vessels do not. During the day, the aground dayshape is three black balls (anchored = one ball). The addition of two red lights at night, or three balls by day, is the definitive indicator of a vessel that is aground rather than merely anchored.
- What is the difference between aground lights and NUC lights?
- Both a vessel aground and a NUC vessel show two all-around red lights in a vertical line. The difference: an aground vessel also shows anchor lights (all-around white); a NUC vessel does not show anchor lights (and shows no masthead lights either). The dayshapes are also different — three balls for aground versus two balls for NUC.
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